Fuel injection device for internal combustion engines

ABSTRACT

A fuel injection device for internal combustion engines in which a fuel injection valve has a tappet which is actuated by an injection valve member and defines a control chamber that is supplied continuously with high fuel pressure via a throttle and can be relieved via a control valve and an outflow conduit. To that end, the control valve has a valve member, which is actuated by a piezoelectric element in such a way that the valve member is moved toward the control chamber when the outflow conduit opens. In the closing position, the valve member is urged in the closing direction by the pressure in the control chamber.

PRIOR ART

The invention is based on a fuel injection device for internalcombustion engines. In a fuel injection device of this type, known fromBritish Patent GB 1 320 057, the outflow conduit coming from the controlchamber discharges into a collection chamber, which communicates with arelief chamber via a relief line leading onward. The valve seat for thevalve member of the control valve is provided at the inlet of theoutflow conduit into this collection chamber. As its drive mechanism,this valve member has a piezoelectric element and is embodied as a valvemember with a conical sealing face. This valve performs the function ofcontrolling the pressure in the control chamber, taking into account thefact that if a piezoelectric element is to function operationallyreliably, it cannot be acted upon except by pressure. In this regard,the closing force transmitted by the valve seat and the resultant force,which is exerted on the valve member from the pressure relief via thecross section of the outflow conduit, act upon the piezoelectricelement. Some of the work capacity of the piezoelectric element is thenlost, because it has to furnish of the closing force.

Advantages of the Invention

The fuel injection device according to the invention, has the advantagethat the closing force required for tightly closing the control valveneed not be brought to bear by the piezoelectric element but instead isgenerated by the pressure in the control chamber. A high adjusting forceto be brought to bear by the piezoelectric element is necessary only foropening the valve, and once again the piezoelectric element is actedupon by the adjusted pressure in the control chamber. As soon as thevalve has opened, the force counteracting the adjusting motion or theopening of the control valve is rapidly diminished, so that in this caseas well the piezoelectric element does not undergo any substantialstress. Thus in the embodiment of the invention the piezoelectricelement that actuates the control valve can be substantially smaller,and the requisite energy can be kept slighter. In the closing positionof the valve, the result is a self-sealing function, because of the factthat in this position, the high fuel pressure delivered via the inletalways prevails in the control chamber.

In an advantageous further feature, the space required for the adjustingmotion of the valve member in the opening direction is reduced to theregion of a recess, so that the diameter of the control piston can bekept small, which in turn has the advantage that higher speeds of thefuel injection valve member can be attained, since the volumetric flowto be forced in and out of the control chamber is less.

In another advantageous feature, two valve seats in line with oneanother are provided in the course of the outflow for relieving thepressure of the control chamber via the outflow conduit. Upon anadjusting motion of the valve member in the direction of the controlchamber, the valve formed by the valve member and the first valve seatis opened, and as a consequence the valve formed by the valve member andthe second valve seat is closed. When the valve member rests with itssealing face on the first valve seat, the pressure in the controlchamber is built up in the sense of closing the fuel injection valve. Ifthe injection valve is to move to the opening position, then upon anactuation of the piezoelectric element the valve member lifts up fromthe first valve seat. In this process, it can remain in an intermediateposition, in which the flow cross section at both valve seats is opened.In this position, the injection valve member of the fuel injection valvecan move to the opening position, so that a fuel injection takes placethat is determined by the length of time that the valve member of thecontrol valve remains in this position. Conversely, if the piezoelectricelement is triggered such that it can execute its full actuation stroke,then after the cross section at the first valve seat opens the valvemember of the control valve comes into contact with the second valveseat, so that in this position again the control chamber is blocked onthe relief side. However, a brief relief of the control chamber takesplace for the duration of the motion from the first valve seat to thesecond valve seat, during which a brief injection event is madepossible. This injection event is utilized for a preinjection. For theensuing required main injection, the valve member can then be put in theintermediate position between the two valve seats, and to terminate themain injection it can be returned to the first valve seat again, underthe joint influence of the high pressure that builds up in the controlchamber. With this embodiment, an especially advantageous additionalpossibility of controlling minimal preinjection quantities at minimaleffort and expense is achieved.

In a further advantageous feature, the second valve seat is embodied onan elastically deformable intermediate part. This has the advantage thatthe requisite work capacity of the piezoelectric element, as a drivemechanism for the valve member of the control valve, can be kept evenslighter. If the valve member of the control valve, after the crosssection at the first valve seat is opened, comes into contact with thesecond valve seat, then a differential pressure is present at theelastically deformable intermediate part. On the side remote from thecontrol chamber, pressure relief to the relief chamber is available,while the high pressure prevails when the cross section at the secondvalve seat in the control chamber is closed. Because of this forceratio, the intermediate part can now deform and move in the direction ofthe drive side of the valve member of the control valve. This reducesthe stroke that the piezoelectric element must execute to open the crosssection at the second valve seat, in order then to relieve the controlchamber in order to furnish the main injection. If the valve member tothat end lifts up from the second valve seat, then because theunilateral force exerted on the deformable intermediate part isrescinded, this intermediate part is returned to its normal position,thus bringing about fast opening of the relief cross section.

An especially advantageous embodiment comprises the pressure proofembodiment of the surroundings of the tappet by means of advantageoushigh-pressure carrying of fuel to the pressure chamber of the fuelinjection valve in the form of a longitudinal conduit in the fuelinjection valve. From there, the inflow conduit can advantageously beextended into the solid housing.

In particular, advantageous features of the sealing faces at the valvemember of the control valve are provided.

DRAWINGS

In the drawing, seven exemplary embodiments of the invention are shownand will be described in detail in the ensuing description. FIG. 1 showsa schematic view of a fuel injection device with supply from ahigh-pressure reservoir and with a fuel injection valve of a known type,controlled by a control valve; FIG. 2 is a fragmentary section throughthe fuel injection valve according to the invention corresponding todetail A in FIG. 1 and showing the control chamber and a valve member ofthe control valve, the valve member being driven in a piezoelectricelement not otherwise shown; FIG. 3 shows a second exemplary embodimentof the invention, having a control valve that has a first and a secondvalve seat and has a modified form of the course of the outflow conduit;FIG. 4 shows the injection valve stroke referred to the adjusting strokeof the control valve member; FIG. 5 shows a third exemplary embodimentin a modification of the exemplary embodiment of FIG. 3, having a secondvalve seat that is disposed on an elastically deformable intermediatepart, shown in a first position of the valve member of the control valveon the first valve seat; FIG. 6 shows the control valve with the valvemember, located on the second valve seat in the closing position, in amodified form, with an elastically deformable intermediate part providedas in FIG. 5 and with an exaggeratedly shown deflection of thisintermediate part in response to the differential pressure prevailing atit; FIG. 7 is a graph of the courses of motion of the valve seat at theintermediate part and of the adjusting stroke of the valve member,associated with the course of motion of the injection valve member; FIG.8 shows a fifth exemplary embodiment of the invention, with a modifiedversion of the second valve seat and of the second sealing face,cooperating with it, on the valve member; FIG. 9 shows a sixth exemplaryembodiment of the invention with a valve member embodied in multipleparts; and FIG. 10 shows a seventh exemplary embodiment with anadvantageous embodiment of the valve housing and an advantageousdisposition of the inflow conduit to the control chamber.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

A fuel injection device, with which a wide variation in fuel injectionat high injection pressures and at little effort and expense and inparticular with very exactly controllable instants of injection andinjection quantities is possible and realized by a so-called common railsystem. Such a system furnishes a different kind of high-pressure fuelsource from that provided by the usual high-pressure injection pump.However, the invention can be used both in this so-called common railsystem and in a fuel injection pump. The common rail system is givenpreference.

In FIG. 1, for a common rail pressure supply system in the form of ahigh-pressure fuel source, a high-pressure fuel reservoir 1 is provided,which is supplied with fuel by a high-pressure fuel feed pump 2 from afuel tank 4. The pressure in the high-pressure fuel reservoir 1 iscontrolled by a pressure control valve 5 in conjunction with a pressuresensor 6 via an electric control unit 8. The electric control unit alsocontrols a fuel injection valve 9.

In a known feature, the fuel injection valve 9 has a valve housing 11,which on its end intended for mounting on the engine has injectionopenings 12, whose outlet from the interior of the fuel injection valveis controlled by an injection valve member 14. In the example beingdescribed, this valve member is embodied as an elongated valve needle,which on one end has a sealing face 15 that cooperates with a valve seatlocated on the inside. The valve needle is located inside a pressurechamber 16, inside the valve housing, that communicates through apressure line 17 with the high-pressure fuel reservoir 1. In anenlarged-diameter portion of this pressure chamber, a compression spring19 is axially fastened between a valve plate 20 and the valve housingand urges the injection valve member 14 in the closing direction. Atappet 21 is provided coaxially with the compression spring and rests onone end on the valve plate 20 while on the other it dips into a guidebore 22, where with its face end 23 forms a movable wall, it encloses acontrol chamber 25 with the closed end of the guide bore. Discharginginto this control chamber is an inflow conduit 26, in which there is athrottle 27 and which, originating at the pressure chamber 16, alwaysfurnishes fuel at high pressure to the control chamber 25 via thethrottle 27. From the control chamber 25, an outflow conduit 29 leadscoaxially with the tappet 21 away from the face end opposite the tappet;the outflow conduit discharges into a relief chamber 30 inside the valvehousing 11, and this relief chamber leads via a relief line 31 extendingonward to a capacious relief chamber 32, which for example may be thefuel tank 4.

In this known injection valve, the mouth of the outflow conduit 29 intothe relief chamber 30 is controlled by a valve member 34 of a controlvalve 36, which is embodied as a seat valve; this valve member can bemoved into the closing or opening position by a piezoelectric element35.

The known fuel injection device functions as follows:

By means of the high-pressure fuel feed pump 2, preferably driven insynchronism with the engine, fuel is fed out of the fuel tank 4 into thehigh-pressure reservoir 1, whose pressure is set to a preferablyconstant value, via the pressure control valve 5 in conjunction with thepressure sensor 6. This value can also be changed as needed. The fuelavailable from this high-pressure fuel reservoir supplies a plurality offuel injection valves of the type described. As long as the valve member34 of the control valve 36 is in the closing position shown, thenbecause of the high fuel pressure delivered via the pressure line 17,this high pressure is maintained in the control chamber 25 as well, andthis pressure, in addition to the compression spring 19, now acts viathe movable wall 23 upon the valve member 14 with a closing force, sothat the injection valve member 14 is moved to the closing position andremains in this position. However, if the control valve 36 is opened,then the control chamber 25 can be relieved via the outflow conduit 29.Because of the decreasing pressure in the control chamber, the closingforce of the compression spring 19 no longer suffices to keep theinjection valve member 14 in the closing position counter to the highfuel pressure engaging a sealing face 41 of the valve member, and hencethis valve member moves to the opening position. Conversely, if thevalve member 34 of the control valve 36 closes in the outflow conduit 29again, then the high fuel pressure immediately resumes in the controlchamber 25 and then returns the injection valve member 14 to the closingposition, and the fuel injection is thus terminated.

In order to improve the mode of operation of this known fuel injectiondevice, the control valve has now been improved according to theinvention. The details in which the invention is realized can be learnedfrom the following drawing figures. FIG. 2 shows a detail of a fuelinjection valve of the basic type shown in FIG. 1, and FIG. 2corresponds to a detail A of this fuel injection valve. Once again, theface end 23 is embodied as a movable wall on the tappet 21 that enclosesthe control chamber 25. The inflow conduit 26 with the throttle 27discharges into the control chamber, laterally of the circumferentialwall of the guide bore 22, in such a way that the inflow is not closedby the tappet in any of its positions. On the face end 37 of the guidebore 22 opposite the face end 23 of the tappet, the outflow conduit 129leads away, via a recess 38 in this face end 37. The transition from thecircular-cylindrical recess 38 to the outflow conduit is made via aconical valve seat 39, which is initially adjoined by a cylindricalintermediate chamber 40 coaxial with the tappet 21, from which chamberthe relief conduit then leads laterally away; a second throttle 42 isalso disposed in the outflow conduit 129. Together with the firstthrottle 27, this determines the behavior of the pressure relief of thecontrol chamber over time.

Now cooperating with the valve seat 39 is a valve member 44 of formmodified compared with the valve member 34 of the control valve 36 ofFIG. 1. This modified valve member has a valve tappet 45, which isguided in a bore 43 of the valve housing 11 and is coupled, on its otherend not shown here, to the piezoelectric element 35. On its endprotruding into the recess 38, this valve tappet has a head 46, on whicha conical sealing face 47 pointing toward the valve seat 39 is provided.In the closing position, shown, of the control valve 36, which sealingface 47 rests on the valve seat 39, so that via the fuel flowing inthrough the inflow conduit 26 a high pressure builds up in the controlchamber 25 and keeps the injection valve member 14 in the closingposition. In this position, the head 46 is acted upon by the pressureprevailing in the control chamber 25, which also keeps the valve memberin the closing position without actuation by the piezoelectric element.To open the control valve, the piezoelectric element is actuated, insuch a way that the head 46 moves farther into the recess 38 anduncovers the flow cross section at the valve seat. In the initial phasethis is effected first counter to the high pressure in the controlchamber. As soon as the valve member has lifted slightly from the valveseat 39, pressure equilibrium is established at the valve member, sothat for the further opening stroke relatively little opening work mustbe exerted at the piezoelectric element. The control chamber isrelieved, and the injection valve member 14 opens. In the process, thetappet 21 as shown moves upward toward the face end 37. By means of achamfer 24 on the face end 23 of the tappet 21 and an opposed annularrecess 28 in the face end 37, a residual chamber is formed that acts asa hydraulic stop. In the region of this residual chamber, a residualsurface area of the tappet 21 always remains exposed to the high fuelpressure delivered via the inflow conduit 26. Between the end face 23and the end face 37 in the region between this residual chamber and therecess 38, a throttle gap remains that uncouples the relieved recess 38from the residual chamber and serves the purpose of building up pressurein the recess 38 as well after the closure of the valve realized at thevalve seat 39 and the valve member 44.

Introducing the inflow conduit 26 into the annular recess 28 that formspart of the residual chamber offers the substantial advantage that theinflow conduit 726 shows in FIG. 10 can be made obliquely to the axis ofthe tappet 721, beginning at a bore 59 that extends parallel to the axisof the injection valve and serves to supply pressure to the pressurechamber 16. If the injection valve housing is divided at the transitionto the relief chamber 30 (FIG. 1), then advantageously the inflowconduit 726 can be drilled obliquely to the residual chamber 738, fromthe mouth 61 of the parallel bore 59, beginning at this dividing plane60. This has the substantial advantage that around the control chamber725, the solid injection valve housing is preserved, and no walldeformations caused by the high pressure prevailing in the high-pressureinlet can deleteriously affect the play in the fit between the guidebore 722 and the tappet 721. In particular, no annular chamber formed bya separate insert, from which the inflow conduit would have to deliverhigh-pressure fuel to the control chamber, as shown in European PatentApplication EP A1 0 661 442, is necessary. In this reference, theguidance of the tappet is provided inside an insert that is surroundedby an annular chamber exposed to the high pressure and thus divides thecontrol chamber from the annular chamber with a slight wall thickness.

With this feature, it is already possible at relatively little effort orexpense with regard to the piezoelectric element 35 that actuates thecontrol valve to perform reliable, fast control of injection events.Because the valve member presents high resistance to the piezoelectricelement only at the moment of opening but subsequently, because of thepressure relief in the control chamber 25 these resistances becomepractically null, the piezoelectric element need merely be designed forthis special loading situation.

In a modification of FIG. 2, the outflow conduit 229 in FIG. 3 can alsolead laterally away from the control chamber 25. FIG. 3 moreover shows afurther advantageous feature of the invention, which is that the valveseat, here provided analogously to FIG. 2, is now a first valve seat139, which is again bordered by the intermediate chamber 40, but fromwhich then the outflow conduit 229 leads via a second throttle 142 tothe relief chamber. Besides this first valve seat 139, a second valveseat 49 is now provided, coaxially with the first valve seat 139 andopposite it on the side toward the control chamber 25. To that end, inan intermediate region, the outflow conduit 229 has a valve chamber 50,into which the for instance spherically embodied head 146 of the valvemember 144 can plunge. Instead of this spherical form, a form as shownin FIG. 2 is also entirely possible, with a conical sealing face 47 asthe first sealing face and, shown as a possible alternative in FIG. 2for use in FIG. 3 by a dashed reference line, a second, likewise conicalsealing face 52 opposite the first.

In FIG. 3, with a conical head, the first sealing face 147 is embodiedtoward the side of the first valve seat 39, and opposite it a secondsealing face 152 is realized in a continuation of the spherical form.This second sealing face, upon actuation of the valve member 144, isbrought into contact with the second valve seat 49, and in this positionthe valve member 144, after an intervening opening of the outflowconduit 229, closes this conduit again. Over the duration of the strokeof the valve member 144 from its position, shown in FIG. 3, on the firstvalve seat 139 to the second valve seat 49, a relief of the controlchamber 25 occurs such that the injection valve member can briefly open.If the valve member rests with its second sealing face 152 on the secondvalve seat 49 again, then the pressure in the control chamber 25 buildsup again very rapidly, and the fuel injection valve closes. Thisembodiment has the very substantial advantage that in a single sequenceand direction of motion upon actuation of the valve member 144 by thepiezoelectric element 35, an opening and reclosure of the relief linewith intermediate relief of the control chamber can be performed, whichmakes it possible to achieve very short relief times. This is veryhelpful in interrupting injection between a preinjection and an ensuingmain injection. While for such a procedure in all the known versions afirst back-and-forth motion of the valve member was required to create apreinjection, and a second back-and-forth motion of the valve member wasrequired to determine the main injection, it is now possible by means ofa single back-and-forth motion of the valve member to control both thepreinjection and the main injection by injection interruption.

FIG. 4 to that end shows the stroke course of the injection valve member14 and associated with it the stroke course of the valve member 144 ofthe control valve over time. In the upper portion of the graph the briefopening of the injection valve for performing the preinjection VE can beseen and then an injection interruption SU, followed by the opening ofthe injection valve for the main injection HE. In the lower portion ofthe graph it can be seen that from the starting position, where thestroke length is 0, the valve member 144 executes a stroke over whichthe preinjection occurs. At the stroke length he, this preinjection isended, and the greatest deflection of the valve member 144 is alsoachieved. After remaining in this terminal position for the period SU,the return of the valve member 144 to an intermediate position ZS takesplace, in which the cross sections at the two valve seats 139 and 49 areopened for the execution of the main injection HE, and this is followedby the final return to the first valve seat 139. In this version, thevalve seats 139 and 49 are preferably coaxially in line with one anotherand are coaxial to the valve tappet of the valve member 144. In thisway, one seat valve on each of the two valve seats is realized.

To reduce the demands made of the piezoelectric element for executingthe adjusting motion of the valve member, in a further refinement of theexemplary embodiment of FIG. 3 the second valve seat is disposed as avalve seat 149 on an elastically deformable intermediate part 55. Thispart takes the form of a disk, for instance, which is preferably ofmetal and is tightly fastened between two halves of the valve housing11. Coaxially to the tappet 21 or to the valve member 244, it has athrough bore 56, that connects the valve chamber 150 with the controlchamber 125.

The entrance of the through bore 56 into the valve chamber 150 isembodied as a second valve seat 349, at which the second sealing face352 of the valve member 344 comes tightly to rest in its maximallydeflected position. The head 346 of the valve member 344 has a conicalface as its first sealing face 347, and a spherical face as its secondsealing face 352, in a modification of the exemplary embodiment of FIG.3. However, a configuration of the head 46 as in FIG. 2 could also beused here. On the side toward the control chamber 125, the elasticallydeformable intermediate part has an annular recess 57, which isconcentric with the through bore 56 and with which it is attained thatthe elastically deformable intermediate part can be more easilydeflected, beginning at this annular recess 57, in particular upwardtoward the valve member 344. However, this property can also be attainedby other kinds of reduction of the thickness of the intermediate part.In FIG. 6 this situation of the deflection of the intermediate part isshown, but there in terms of a valve having a head 446 of the valvemember 444 that is spherical as in FIG. 3. If the head 446 comes intocontact, by its second sealing face, with the second valve seat 349,then the high pressure prevailing in the high-pressure fuel feed pumpcan build up in the control chamber 25. If, in the position of the valvemember 344 shown in FIG. 5, the valve chamber 150 was exposed to thesame pressure as the control chamber 125, in the position of FIG. 6 nowdifferent pressures prevail, such that the elastically deformableintermediate part 55 is now deformed toward the valve member 444. Thisevent is illustrated in FIG. 7. In graph portions associated with oneanother and located one above the other, the reciprocating motion of theinjection valve member 14 is shown at the top, again having the regionof the preinjection VE, the injection interruption SU, and the maininjection HE. In the lower part of the graph, curve M represents themotion of the elastic intermediate part. At an outset position hmO,referred to the adjusting path of the valve member 444, the intermediatepart with the second valve seat 349 is moved into a position hml. Thisbegins at the end of the reciprocating motion of the valve member 440,when the valve member, beginning at the outset position V0, assumes theposition hm0 in contact with the intermediate part. Once this positionis reached, the valve member together with the second valve seat 349 ofthe intermediate part is brought, under the influence of the now-arisingdifferential pressure, to the position hm1 and remains there as long asthe valve member 444 is in contact with the second valve seat 349. Afterthat, once the valve member 444 has lifted away from the second valveseat 349 again, it returns to its outset position hm0, and the valvemember 444, as in the graph of FIG. 4, moves to an intermediate positionZS, in which the control chamber 125 is relieved and the main injectionis completed. After that, the valve member returns to its terminalposition V0. In the region in which the diaphragm deflects in thedirection of the stroke hm1, the valve member can also be deflectedbackward, so that its stroke, from the original terminal position hm0,returns to a common terminal position hm1. The stroke to be executed bythe valve member 444 afterward for complete opening is thus reducedcompared with the version of the curve v1, shown in dashed lines, thatwould result without elastic deflection of the intermediate part. Sinceimmediately after the second valve seat 349 lifts away from its seatboth parts, that is, the valve member 444 and the elastically deformableintermediate part 55, execute a stroke in the opening direction, theresult here is a very fast relief of the control chamber 125 for theexecution of the main injection. The demands made regarding the maximumstroke length of the piezoelectric element are thus less, since theactual closing force to the second valve seat 349 is establishedtogether with the deformation of the elastically deformable intermediatepart. This is very substantially advantageous, since the size of apiezoelectric drive mechanism and the energy furnished by the purposeincrease substantially with the length of the required adjusting stroke.In the way described here, the required stroke length can be reduced forthe same performance of the control valve.

In the above description, various embodiments of the valve member havebeen shown. FIG. 8 also shows a variant with a head 546 of the valvemember 544, which has one conical sealing face 547 and 552 as its firstand second sealing face, respectively. The valve seats are embodiedaccordingly. In the final analysis, it is also possible instead of aconical second sealing face 552 to provide a flat-seat sealing face,with a correspondingly embodied second valve seat.

In a further feature in accordance with a sixth exemplary embodiment,the valve member 644 of FIG. 9 can be embodied in two parts, in such away that it has a head 646, which has the first sealing face 647 and onthe side remote from this sealing face a guide face 59, on which asecond valve member 60 hydraulically coupled with the valve member 644is guided. This second valve member is embodied as a ball in thisexample and cooperates with a spherical but preferably a conical secondvalve seat 649. In the position shown for the valve member 644 on thefirst valve seat 639, the ball 60 is held in contact with the valvemember 64 by the pressure in the control chamber 625. Upon actuation,the ball is guided into contact with the second valve seat 649. Withsuch a ball, which is a standard part, a tight fit with the valve seatcan be achieved favorably.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

We claim:
 1. A fuel injection device for internal combustion engines,having a high-pressure fuel source (1) which supplies a fuel injectionvalve (9) with fuel, the fuel injection valve having an injection valvemember (14) for controlling injection openings (12), a control chamber(25) which is defined by a movable wall (23) connected at leastindirectly to the injection valve member (14), an inflow conduit (26),dimensioned by means of a throttle (27) which throttles fuel from thehigh-pressure fuel source (1), an outflow conduit (29) defined by amaximal outflow cross section to a relief chamber (30), at said outflowconduit, a valve seat (39) is formed that is controlled by a sealingface (47) of a valve member (44, 46) of a control valve (36) that isactuated by a piezoelectric element (35), the valve seat (39) isdisposed pointing toward the control chamber (25) on the outflow conduit(129), and the piezoelectric element (35) lifts the valve member (44,46) from the valve seat (39), counter to a pressure prevailing in thecontrol chamber (25), in order to open the outflow conduit (129) towardthe control chamber (25), and the valve member (44, 46) is urged in aclosing direction by the pressure in the control chamber (25).
 2. A fuelinjection device in accordance with claim 1, in which the outflowconduit (129), on the face end (37) opposite the movable wall of thecontrol chamber (25), discharges into the control chamber (25), and arecess (38) that receives the valve member (44, 46) in the open positionthereof is disposed between the movable wall (23) and the face end (37).3. A fuel injection device in accordance with claim 1, in which thevalve seat on the outflow conduit is a first valve seat (139), and onthe control chamber side of this first valve seat a second valve seat(49) is provided, which defines the outflow cross section of the outflowconduit (229) and is closed by an additional second sealing face (152),said sealing face is moved by the valve member (144, 146) under theinfluence of the actuation by the piezoelectric element, after the valvemember (144, 146) has lifted from the first valve seat (139).
 4. A fuelinjection device in accordance with claim 3, in the spacing of the firstvalve seat (139) from the second valve seat (49) is dimensioned suchthat in an intermediate position of the valve member (144, 146), theoutflow cross sections at both valve seats are opened.
 5. A fuelinjection device in accordance with claim 4, in which the valve seats(139, 49) are disposed coaxially to one another.
 6. A fuel injectiondevice in accordance with claim 5, in which the valve member (44, 144,344, 44, 544, 644) has a head (46, 146, 346, 446, 546, 646) that carriesat least one of the sealing faces (47, 52, 152, 147, 347, 352, 547, 552,647), which head is disposed at an end of a tappet (45) that protrudesthrough the cross section of the outflow conduit bounded by the firstvalve seat (39, 139) and that between the tappet and the first valveseat defines the largest outflow cross section.
 7. A fuel injectiondevice in accordance with claim 6, in which the second sealing face(152) and the second valve seat (49) together form a seat valve, and thevalve member (144, 146), when the seat valve is closed, is urged in theopening direction by the pressure in the control chamber (25).
 8. A fuelinjection device in accordance with claim 3, in which the second valveseat (349) together with a cross section leading onward to the controlchamber (25) is embodied on an elastically deformable intermediate part(55), in a region of the second valve seat (349), and said elasticallydeformable intermediate part is fastened by its edges firmly betweenparts of the housing (11) of the fuel injection valve.
 9. A fuelinjection device in accordance with claim 8, in which the intermediatepart (55) is embodied as a diaphragm.
 10. A fuel injection device inaccordance with claim 9, in which the diaphragm is a metal diaphragm,whose deformability is increased by regions of reduced diaphragmthickness, by means of annular recesses (57) located concentrically tothe second valve seat.
 11. A fuel injection device in accordance withclaim 1, in which a maximum outflow cross section is formed by athrottle (42).
 12. A fuel injection device in accordance with claim 3 inwhich the first valve seat is embodied as a conical valve seat (39,139).
 13. A fuel injection device in accordance with claim 12, in whichthe second valve seat is embodied as a ball seat.
 14. A fuel injectiondevice in accordance with claim 12, in which the second valve seat (552,649) is embodied as a conical seat.
 15. A fuel injection device inaccordance with claim 12, in which the second valve seat is embodied asa flat seat.
 16. A fuel injection device in accordance with claim 12, inwhich the second sealing face is embodied on a part (60) actuated by thevalve member, which part comes to rest on the valve member (644, 646) inresponse to the pressure in the control chamber (25).
 17. A fuelinjection device in accordance with claim 16, in which the secondsealing face is embodied on a ball (60) that is guided on a guide face(59) of the valve member (644, 646).
 18. A fuel injection device inaccordance with claim 6, in which the tappet (45) is guided in a bore(43) extending coaxially to the valve seats, between said bore and thefirst valve seat a chamber (40) is defined by the outflow conduit (129)which leads to the relief chamber (30, 32, 4).
 19. A fuel injectiondevice in accordance with claim 2, in which the valve seat on theoutflow conduit is a first valve seat (139), and on the control chamberside of this first valve seat a second valve seat (49) is provided,which defines the outflow cross section of the outflow conduit (229) andis closed by an additional second sealing face (152), said sealing faceis moved by the valve member (144, 146) under the influence of theactuation by the piezoelectric element, after the valve member (144,146) has lifted from the first valve seat (139).
 20. A fuel injectiondevice for internal combustion engines, comprising a high-pressure fuelsource (1), a fuel injection valve (9) which is supplied with fuel, thefuel injection valve having an injection valve member for controllinginjection openings (12) and having a control chamber (25) which isdefined by a movable wall (23), said movable wall is connected at leastindirectly to the injection valve member (14) and which has an inflowconduit (726), dimensioned by means of a throttle which throttles fuelfrom a high-pressure source, an outflow conduit (29), connected with arelief chamber (30), a valve seat (39) is formed at said outflowconduit, fuel flow is controlled by a sealing face (47) of a valvemember (44, 46) of a control valve (36) that is actuated by apiezoelectric element (35), the inflow conduit is supplied with fuel athigh pressure from a pressure conduit (59) that extends longitudinallyin the fuel injection valve, and the injection valve body is embodied inmultiple parts, with a dividing plane (60) into which the pressureconduit discharges and from which the inflow conduit (726) is drilledthrough a mouth (61) of said pressure conduit into the dividing plane,and in an uppermost position of the movable wall (721), an annularresidual chamber (738) remains between the face end of the bore (722)that receives the movable wall and the movable wall itself, and theinflow conduit (726) discharges into said residual chamber.